Enclosed moist pad assembly with removable cover

ABSTRACT

A multiple part assembly includes an enclosure for a moist pad member. The assembly included a cup-shaped container within which the pad member is located. A heat seal secures the outer edge of the pad member to the container. A support is secured encircling the container and includes an annular backing member encircling the open end thereof. The backing member is adhesively affixed and peelable for the support. A plastic film cover overlies the pad member and adjacent portion of the backing member. An encircling fusion seal joining the plastic film cover to the backing member for removal of the cover with the backing member. A plastic heating tool includes an annular or circular tool element formed of appropriate material which is responsive to an inductive field for self-generation of heat within the tool for attaching the pad to the container.

This is a divisional application of application Ser. No. 234,517, filedFeb. 20, l981, now U.S. Pat. No. 4,380,484.

BACKGROUND OF THE PRESENT INVENTION

Plastic elements in the form of films and preformed members are widelyused in packaging as well as structural constructions. The plasticmember is often conveniently attached to another member particularlyanother plastic member by a bond, with or without an interposed medium.

The processing and working of plastic materials and elements thusgenerally involve various cutting, forming, sealing and bondingfunctions. For example, flat plastic parts may be formed from film-likematerial by die cutting. Multiple plastic layers and thin plastic filmsmay be attached by applying of heated elements. For example, sealing ofplastic objects to each other, particularly with a straight line bond,is often made using a metal wire, or narrow band of material, covered bya protective plastic release layer. The wire-like element is placed inengagement with the plastic layers and an electric current is passedthrough the element. The current flow results in resistance heating theelement and the temperature of the wire increases to a temperatureoperable to fuse the plastic layer or layers to form a thermal fusionbond. After the necessary time of heating, the current is removed, thejoined elements allowed to cool, thereby simultaneously cooling of theplastic to complete the seal or connection. Cutting and joining oflayers may also be accomplished employing a neated elegant. For example,U.S. Pat. No. 3,441,460 discloses a system wherein the film layers areheld between a pair of clamping jaws. A resistance heated knife is moveddownwardly between the clamping jaws into engagement with the plasticfilm. The knife functions to simultaneously sever the plastic layers bymelting thereof and creating an interconnecting plastic bead on thesevered edges.

Another significant method of bonding plastic elements is the use ofinductive heat generation in the plastic elements. For example, thepresent inventor is active in the development and application of aunique inductive heating method using particulate material embeddedwithin one or more plastic elements and which responds to a highfrequency magnetic field to create heat within the element as the resultof hysteresis losses. The hysteresis loss method rapidly heats theplastic to the level necessary to create a firm and reliable fusionbond. Other forms of inductive heating of the plastic member have alsobeen suggested for bonding. For example, U.S. Pat. No. 3,909,326discloses a method of attaching a film cover to one end of a tubularmember, such as an open-mouth container. In such system, the packagingor covering member includes a metallic film having a heat sealablematerial on one surface which is held in firm engagement with the openedge of the container. The covered container is moved past an inductionheating coil which activates the metallic film through inductive effectsto generate heat within the sealing member of an appropriate level tomelt the heat sealable material and heat seal the member to thecontainer. The prior art has even suggested the use of ultrasonicsystems for attaching one plastic film member to another member; forexample, as shown in U.S. Pat. No. 3,970,490 which issued July 20, 1976.

The above and similar teachings have been suggested but there remains aneed for a reliable method of working thin plastic films and plasticmembers for cutting and/or sealing to another member, and eliminatingthe need for expensive heat generating material such as aluminum foil inthe assembly.

SUMMARY OF THE PRESENT INVENTION

The present invention is particularly related to an inductively heatedapparatus for working and processing plastic elements, and in particularcutting, sealing and like working of a relatively thin or film-likeplastic element to create firm attachment to another member. Generallyin accordance with the teaching of the present invention, the apparatusincludes a tool unit having an inductively heated cutting and/or sealingend surface and includes a forced cooling means for controllingconduction of heat from the working end surface of the tool unit. Thecooling is preset in relationship to the plastic material and cycling toprovide an unexpected satisfactory and effective means of operatingvarious tool units for purposes of cutting, sealing and the like. Thisinvention has been found to provide effective, rapid and reliablerelease of the tool working surface from the plastic member whilepermitting rapid cycling.

In a preferred embodiment of the invention for forming of disc-likeelements and the like, the tool unit consists of an appropriately shapedannular or circular tool member formed of appropriate material which isresponsive to an inductive field for self-generation of heat within thematerial of the tool member. The tool member is secured to a heattransfer member which is coupled to a forced cooled element which coolsthe transfer member and thereby the tool member. The transfer member aswell as the cooled element permits cooling at a selected retarded rateand provides for the desired interaction of the tool member and theprocessed plastic which creates effective heating of the tool and theplastic while cooling the tool for release purposes, thereby permittinga desired cycle time.

In accordance with a further feature of one embodiment of the presentinvention, the tool is specially constructed for attaching a film-likeplastic member in overlying relationship to another base member orarticle, or other similar application. In this embodiment, the tool unitis forced downwardly onto a stretched film-like plastic member whichforces the plastic sheet downwardly to the base member. The tool unitincludes an inductively activating unit coupled to the tool element andactivated to inductively heat the tool element which functions tosimultaneously thermally sever the aligned portion from the film-likeplastic sheet and seal it to the opposed base member. The film sheet isplaced under tension during the severing and promotes a clean separationof the aligned portion. The same tool unit can of course beappropriately applied to a preformed member for sealing thereof to anopposed member.

In using the regulated cooled tooling, the inventors have further foundthat optimum and unusually satisfactory and unexpected results areobtained by initiating the cycle with the tool significantly below thefusion temperature. The tool element is inductively activated to rapidlyraise the temperature of the tool substantially above the fusiontemperature of the plastic film, where it is held at least momentarily,then deactivated and rapidly cooled below the fusion temperature.

The induction heating and cutting assembly may in one embodiment includea support plate with an opening through which the tool unit moves. Aloop coil is intimately attached to the plate and connected to asuitable high frequency source of power. The plate is formed with aradial slit or opening to form a discontinuity such that the highfrequency current flows in a loop pattern in the periphery of theopening. The high frequency current creates an induced current in theadjacent working end of the tool unit. Magnetic and ohmic losses in thetool element generate selfheat within the tool. By appropriate designand excitation, the tool element can be held at a steady but elevatedtemperature or suddenly increased in temperature over a closelycontrolled time period, thereby adapting the tool unit for various formsof processing and work.

It has also been found desirable in the construction of the tool toappropriately shape the end of the working tool to provide anappropriate mass for heat transfer while maintaining an appropriateworking end to provide the necessary heat and cooling during eachprocessing cycle. The tool element may be advantageously constructedhaving a larger lateral working end than the heat transfer element. Theenlarged lateral end is then closely spaced to the inner peripherialsurface of the opening in the inductively heating assembly whichconcentrates the inductive energy within the working end of the tool andestablishes a more rapid increase in the excitation, and therefore thetemperature, of the tool element.

The cutting tool unit of the invention might also be advantageouslyapplied to die cutting. Thus, the tool unit may be moved downwardlyforcing a plastic film into engagement with a backing support torapidly, thermally sever the film. The engaged tool unit is then rapidlycooled so as to be readily removed or separated from the cut plasticfilm without significant tendency of the plastic to adhere to thetooling.

The tool unit preferably includes a heat transfer element having a highthermal conductivity, such as a copper element, connected to a cooledelement such as a forced cooled plate. The heat transfer element is notsignificantly heated by induced current because of its good electricalconductivity but establishes appropriate controlled transfer of thethermal energy from the working portion of the tool unit. The cooledelement may advantageously be a nonmagnetic stainless steel which has amagnetic or resistance characteristic to retard significant heating byinduced current but also having a sufficiently low thermal conductivityto maintain an appropriate heat sink for controlled removal of heat fromthe transfer element. Such selection and design contributes toconcentrating the induction heating effect within the working end of thetool unit to provide efficient transfer and usage of the energy.

These and similar advantages of the invention as set forth in the abovegeneral discussion of the more significant features of the presentteaching will be more fully understood from the following description ofpreferred embodiments of the present invention. The present inventionprovides a highly improved inductively heated sealing and/or cuttingtool unit for hot working of a plastic element. The structure of theinvention may employ commercially available components and technologyfor commercial, on-line production with high speed, reliable cuttingand/or sealing of plastic elements. The structure may therefore beconstructed at an economically acceptable cost level.

DESCRIPTION OF THE DRAWING FIGURES

The drawings furnished herewith illustrate preferred constructions ofthe present invention in which the above advantages and features areclearly disclosed as well as others which will be readily understoodfrom the following description.

In the drawings:

FIG. 1 is a side view of a diagrammatically illustrated inductionheating apparatus for cutting and sealing a plastic film member to abase support with parts broken away and sectioned to show detail ofconstruction;

FIG. 2 is a top view of the apparatus shown in FIG. 1;

FIG. 3 is an enlarged vertical section of an apparatus shown in FIGS. 1and 2 and taken generally on line 3--3 of FIG. 2;

FIG. 4 is a horizontal cross sectional view of the cutting and sealingelement shown in FIGS. 1-3 and taken generally on line 4--4 of FIG. 3;

FIG. 5 is a reduced view similar to FIG. 3 illustrating a step in thesequence of a cutting and sealing operation;

FIG. 6 is a view similar to FIG. 5 showing the sealing position of theapparatus;

FIG. 7 is a view showing the apparatus moving into the release positionafter completion of the cutting and sealing step;

FIG. 7a is a fragmentary enlarged view of a modified tool end;

FIG. 8 is a view similar to FIG. 3 illustrating a modification of theapparatus for applying a foam cover to a cup-shaped member of a bodyelectrode;

FIG. 8a is an enlarged cross-sectional view of the electrode formed withthe apparatus shown in FIGS. 8-9;

FIG. 9 is a view of the apparatus shown in FIG. 8 with the tool unit inthe cutting and sealing position;

FIG. 10 is a view similar to FIG. 3 illustrating a modification of theinvention for applying a preformed cap to a base support;

FIG. 11 is a plan view illustrating a multiple section apparatus forapplying a flat film-like lid over an open container in combination withan over cap;

FIG. 12 is a vertical section through the apparatus of FIG. 12 at thelid sealing station; and

FIG. 13 is a pictorial view of a clamping element shown in FIGS. 11 and12.

DESCRIPTION OF THE ILLUSTRATED EMBODIMENT

Generally, the drawings furnished herewith illustrate various featuresand embodiments incorporating the teachings of the present inventionwherein an inductively heated apparatus is provided for the cuttingand/or sealing of one plastic member to a second member which willgenerally be of a similar, and at least, a compatible material for heatsealing or joining thereof. The several elements may be single elements,multiple layered elements or the like. The present invention is thusparticularly directed to the method and apparatus for applying of heatsealable material or member to another member in a rapid manner and in amore or less production line installation.

Referring particularly to FIG. 1, an embodiment of the invention isillustrated wherein a thin film cover 1 is secured overlying an article2, supported on a base 3. The peripheral portion of cover 1 is sealed tothe base member 3 for protective enclosure of article 2. In theillustrated embodiment of FIGS. 1 and 2, a conveyor 4 is provided forsupporting a series of spaced base members 3, each of which supports anarticle 2. The conveyor 4 moves relative to a film strip or web 5 fromwhich successive film covers 1 are formed, Conveyor 4 particularlyprovides for sequential positioning of the article-loaded members 3 andthe film web 5 in selective alignment within a cutting and sealingapparatus 6, which is constructed in accordance with the teaching of thepresent invention. The film supply is illustrated as including a web 5of indefinite length of the film material which is supported betweenpowered feed and take-up rolls 7 and 8 to form an aligned film web 5under tension within apparatus 6. Cutting and sealing apparatus 6includes a vertically reciprocal tool unit 9. An induction heating coilunit 13 is coupled to tool unit 9 to heat the working end of the toolunit 9. The tool unit 9 is adapted to move downwardly through the filmweb 5 removing a portion thereof to define the film cover 1 and leavinga hole or opening 9a within the aligned portion of the film web 5. Thus,the uncut scrap portions about hole 9a maintain the longitudinalintegrity of the web 5 for movement through the apparatus 6 to thetake-up roll 8. The tool unit 9 functions to force the film web 5downwardly over the article 2 and the heating coil unit 13 is activatedto cut the cover 1 from the web 5 and to form a fusion or thermal seal10 in the peripherial edge portion of film cover 1 to the base member 3.The seal 10, as illustrated most clearly in FIG. 2, is an encirclingseal to effectively completely enclose article 2, but may of course beotherwise formed; for example, with multiple spaced seal portions.

Referring to FIG. 3, a suitable cutting and sealing apparatus 6 is shownin section and includes a supporting structure including a base plate 11over which the conveyor 4 passes with the base members 3 locatedthereon. The supporting structure is of course adapted to be mounted inany suitable location and provides for horizontal movement of theconveyor 4 therethrough. In the illustrated embodiment, the conveyor 4and web 5 move parallel to each other, and are diagrammatically shown assuch devices can be of any suitable construction and readily provided.Conveyor 4 is shown as a belt-like unit which moves through apparatus 6for loading and unloading the base members 3 with articles 2, as shownin FIGS. 1 and 2, thereon for simplicity of illustration.

A head assembly 12 is secured in overlying relationship to thesupporting base 11 and supports the tool unit 9 for vertical reciprocalmovement toward and away from the supporting base. The induction heatingcoil unit 13 is separately supported on the head assembly 12. Unit 13 isan annular assembly having an opening 14 through which the tool unit 9is moved. A conventional power cylinder 15 is coupled to the tool unit 9and a similar power cylinder 16 is secured to the induction heating unit13 for selective vertical positioning of the structure, as more fullydescribed hereinafter.

More particularly, as shown in FIG. 3, the tool unit 9 is a three pieceassembly which in the illustrated embodiment of the invention isconstructed to provide a round cut for removing the film cover 1 fromthe web 5. Tool unit 9 includes an annular cutting and sealing element17 which functions to cut the plastic film cover 1 from web 5 and thenseal the cover 1 to base 3 overlying article 2. For example, plasticfilm or web 5 is typically a low-density polyethylene and the basemember is formed of a compatible plastic such as another polyethylene orprovided with a similar coating. The tool element 17 is shown as a solidring which is formed of a suitable material for responding to a highfrequency electromagnetic field created by induction heating coilassembly 13. The element 17 may be a ferromagnetic metal such as amartensitic tool steel which is commercially available by theidentifying number H-11 alloy. The described material of element 17 thusis such that in a presence of an electromagnetic field, RF currents flowwithin the metal, the resistance of which is such that ohmic andmagnetic losses appear as heat. Ordinary carbon steel has been used butdoes not have the durability of tool steel.

The ring element 17 is generally L-shaped with an outwardly projectedworking leg or end 18. The outermost portion is formed to define areasonably sharp cutting edge 19, which may be a slightly flat edge toincrease the seal area of seal 10. The opposite side walls or faces ofthe leg 18 are chamfered to gradually separate from the cutting edge 19.The bottom wall or face particularly is tapered or angled slightly tothe horizontal. Angles of 10 to 15 degrees have been used withsatisfactory results. An outer stepped projection might also be used.Thus, the face of the element is preferably closely spaced to the coilunit to concentrate the heat in the outer end. For example, an RFgenerator having 2.5 kW output was connected to energize the severalcoils of three tool units in series. The movement of the tool unit 9downwardly through the film web 5 results in the cutting edge 19 movinginto engagement with the film web 5. The continued downward toolmovement forces web 5 downwardly toward the base member 3. At apredetermined time, the power supply is energized to heat the cuttingelement 17 which results in a thermal severing of film web 5 andformation of cover 1, including the formation of the seal 10 to securesuch severed cover 1 to base member 3.

An annular heat transfer member 21 is secured to the upper end of theannular cutting element 17. The annular heat transfer member 21 is shownas a tubular element having a reduced coupling portion projecting inclosely overlapping relationship to the inner upper end of the annularcutting element 17. The heat transfer member 21 and element 17 areintimately joined as by silver soldering or the like. The above junctioncreates a good thermal transmitting junction and establishes arepeatable controlled heating and cooling of the cutting element 17.

The thermal transfer element or ring 21 can be formed of any suitablematerial which establishes the desired relatively rapid heat transfer.Copper is particularly desirable because it provides good heat transferand has a very low electrical resistance such that ohmic losses areminimum. The transfer element 21 is therefore not heated significantlyby induced currents when in the field of the induction heating coilassembly 13.

A cooled plate 23 is similarly intimately joined to the upper end of theheat transfer member 21, as at 23a. Plate 23 is illustrated as a flatplate member having an undercut portion telescoped into the outer end ofthe heat transfer element 21 and preferably similarly connected as by asilver soldered joint. The plate 23 is formed of a suitable heattransfer material and preferably a material which has a relatively lowresistance such that in the high frequency field, excessive heat is notgenerated. For example, an austenitic stainless steel which iscommercially available as a 304 alloy provides a satisfactory material.Although the resistance of such steel is not particularly low, thematerial heats relatively slowly in the RF field, particularly ascompared to the magnetic steel used in the cutting element 17.

The firm mechanical and bonded contact including the silver soldering orthe like is desirable to establish efficient and predictable rates ofheat transfer through the heat transfer member to the cooled plate,thereby permitting reproducible and predictable operation of the toolunit 9.

Plate 23 is coupled to a suitable cooling unit 24 such as a serpentinecooling tube embedded therein. The cooling tube 24 is connected bysuitable flexible leads 25 to a coolant source 26 for establishingcontrolled heat transfer from the cutting and sealing element 17.

The three-piece tool unit 9 is suitably secured to the power cylinderunit 15 for vertical positioning. The tool unit 9 is shown connected tothe piston rod 27 of the cylinder unit 15 as by a connecting bolt 28which passes through the cooled plate 24. The power cylinder unit 15includes a fixed cylinder connected to the head support assembly 12. Apiston, not shown, within the cylinder is connected to the piston rod 27which projects downwardly to the bolted connection to the tool unit. Thepower cylinder unit 15 is coupled to a suitable pressurized fluid supplyfor power positioning of the tool unit 9 with respect to the base plate11.

The induction heating coil unit 13 is mounted for selective activationand for positioning simultaneously with the movement of cutting element17 for proper excitation of the element 17. The illustrated inductionheating unit 13 includes a support ring 30 in the form of a plate-likemember defining the central opening 14 which is aligned with the toolunit 9. Ring 30 is coupled to the power cylinder unit 16 for selectivevertical positioning with respect to the tool unit 9 and particularlythe cutting and sealing element 17. A single turn cooling coil 31 issecured to the top wall of the support ring 30 and encircles the opening14 in the support. The opposite ends of coil 31 are as diagrammaticallyshown, connected by suitable power leads 32 to a high frequency powersupply 33. A timer and sequence control 33a is shown connected to thecoolant supply 26 and power supply 33 to establish timed operationthereof. Control 33a would also operate the positioning means 15 and 16for the appropriate movement of the elements, such as hereinafterdescribed. The support ring 30 is formed of copper or other highlyelectrically conductive material. The cooling coil 31 is soldered orotherwise intimately attached to the support ring 30 by silver solderingor the like, as at 31a. The cooling coil 31 is a metal tube whichcarries cooling water as well as the energizing current from the powersource 33, which current transfers to and from the ring 30 at the ringconnection. The support ring 30 includes a radial gap or slit 34generally located between the power leads 32 to the cooling coil 31. Theslit 34 prevents circulation of the current and forces the current toflow in a loop pattern 34i a generally in accordance with the split ring30, with the current concentrated in the area of opening 14.

The supply or source 33 may be any suitable high frequency or radiofrequency supply. Typically, with a power source 33 of operatingfrequency of approximately 4 megahertz, and with the illustratedconstruction, the current will tend to flow in the pattern uniformlydistributed about the inside diameter of the opening 14. Although theoperating frequency is not critical, a more uniform pattern was notedwith the higher frequency. Generally, 1.5 MHz has been found to be auseful frequency for practical application. Substantially higherfrequency up to 30 MHz will theoretically operate.

With the cutting element 17 and particularly the leg 18 aligned with thesupport plate or ring 30, the RF current in the support ring 30 inducescorresponding RF current in the adjacent working face of the toolelement 17. The induced current produces ohmic and magnetic losseswithin the tool element 17 and particularly leg 18, resulting in heatgeneration therein. The heat level generated is dependent upon not onlythe frequency of supply 33 and the material of the element 17 but alsothe relative tool dimensions and the velocity of heat transfer or lossof heat through the heat transfer element 21 to the associated cooledplate 23. The factors can be readily controlled in the design of theapparatus and may be designed to vary the heat characteristic. Thus, byvarying the level of the excitation current applied to coil 31 thecutting element 17 can first be held at a relatively low and steady butsomewhat elevated temperature, can secondly be excited to suddenlyincrease the temperature above the ambient or steady state level. Thevariation may be created over a closely controlled period and held forthe necessary period to properly work the film cover 1. Similarly, rapidor slow cooling of the tool element 17 may be created as a result of thedeenergization of the coil 31 and the controlled cooling of the cooledplate 23 and the heat transfer member 21. The tool element 17 andparticularly edge 19 is sufficiently cooled prior to raising of the toolunit 9 to insure clean release of the tool element 17 from film cover 1.

The tool unit 9 is thus preferably specially constructed to confine theinduction heating action of the RF field to the cutting element 17 andparticularly the working portion 18-19 to establish the most efficientuse of the energy. The increased diameter of the working portion 18 ofthe tool element 17 in relationship to the other portions of the toolunit 9 tends to concentrate the energy in the working portions of toolelement 17 more closely adjacent to the induction heating coil assembly13. This tends to concentrate the RF field in the enlarged portion andfurther removes the field from the transfer member 21. The field isthereby primarily placed within the working portion 18 where it isuseful and removed from the heat transfer member 21 where the heatcreated would dissipate as wasted energy and interfere with the functionof heat transfer element 21 during the cooling period after removal ofthe RF field. The working surface of the cutting element may be coveredwith a suitable release material, such as that sold under the trademark"Teflon" or other suitable material, not shown. Such material, however,has a tendency to wear rather rapidly and may require periodicreplacement. Other releasing systems might also be used. For example, alight application of silicone grease applied to the working faceperiodically, such as once a day, can further insure a film-free cleanrelease of the tool element.

Although the present invention may be applied to any form or anymaterials suitable for fusion and thermal attachment to another member,the apparatus has been found to produce unusually satisfactoryattachment of the polyethylene film to a base member having a facingcoating of polyethylene or an olefinic resin coating.

A preferred cutting and sealing sequence is described with respect tothe apparatus shown in FIGS. 3, 5, 6, and 7, as follows. The cutting andsealing tool unit 9 is initially in the fully open position, shown inFIG. 5. The film web 5 is positioned with a continuous portion betweentool unit 9 and an aligned article 2. After location of article 2 inplace, the cylinder 16 may be operated to move the induction coil unit13 downwardly adjacent to or on the conveyor 4. Alternately, in anactual mode practiced, the coil unit 13 and the tool unit 9 weresimultaneously moved downwardly, as presently described.

Power cylinder 15 is actuated to move the tool unit 9 downwardly withthe cutting element 17 moving into engagement with the aligned portionof the film web 5 and simultaneously the power cylinder unit 16 isactuated to lower the induction heating coil unit 13. The inductionheating coil unit 13 is energized just prior to or simultaneously withthe forcing of web 5 onto base 3, as shown in FIG. 6 to provide rapidinductive heating of the cutting element 17, which rapidly heats atleast the working edge or land 19 (FIG. 3) preferably above the meltingtemperature of the film web 5. The working edge 19 thus thermally seversthe cover 1 from web 5 and forces the peripherial edge portiondownwardly onto the base member 3 with the film cover 1 overlying thearticle 2. The force with which the cooled element 17 forces the cover 1to the base 3 is not critical. The force is preferably sufficient toremove any distortion or wrinkles which might develop in the film web 5during its movement and further to stretch the film cover 1 over thearticle 2. The total encirclement of the tool element 17 over thesevered film cover 1 tends to heat the film material, resulting in thesmooth stretching and conforming of the material over the article 2thereby producing a wrinkle free cover. Thus, in addition to providing ahighly effective seal, the apparatus may provide a uniform and smoothcover which is esthetically pleasing.

Tension is preferably formed in the film web 5 during the severing andsealing cycle which is sufficient to pull the film web from the severedfilm cover 1 and allow return of the web 5 to the horizontal position asshown in FIG. 7. The stretching of the web 5 of course also contributesto a clean, sharp and complete severing of the film cover 1 from the web5. After a short dwell sealing period, the tool unit 9 and inductionheating coil assembly 13 are raised from the base member 3 and theconveyor 4 actuated to move the base member 3 with the attached filmcover 1 from alignment with the tool unit 9. The covered article isreplaced with an uncovered article and conveyor 4 again moves to alignthe new uncovered article 2 and base member 3 within the apparatus 6 andthe cycle is repeated.

Although any functional temperature sequence can be used, the inventorshave found that unusually satisfactory and surprising results areobtained by starting with the tool end 18 below the fusion temperatureof the plastic film 5, and may be conveniently cooled to normal roomtemperature of approximately 70 degrees. After contact with the film,energy is supplied to create a rapid rising temperature in the cuttingelement 17. The temperature rises above the temperature necessary tosever the cover 1 from the web 5 and thermally fuse and seal the cover 1to the base 3 under some pressure. While the cutting element is inpressurized sealing engagement with the cover 1, the high frequencypower supply is rapidly decreased or removed. This terminates heating ofcutting element 17 and establishes a controlled but rapid transfer ofthe heat from the element 17 via heat transfer member 21 to the heatsink plate 23. After a short cooling period, the cooled ring end 18 andparticularly edge 19 can be readily removed from the film cover 1without any tendency for the film cover 1 to adhere to the cooledcutting element 17.

For example, in a practical sequence for applying the polyeythelene filmto a base member 3 having a polyeythelene coating, the cycle timeincluded a period of less than one second to move the tool unit 9 andthe heating coil assembly 13 downwardly into alignment and clampingposition. One to four second cutting and heating periods were used andcompletely severed the film cover 1 from the web 5 and firmly sealed thefilm cover 1 to the base member 3. Stretching of the film web 5 duringthe period the tool element 17 moves downwardly contributes to a clean,sharp and complete cutting of the web cover 1 from the web, which thenreturns to the planar position, as most clearly shown in FIG. 7. Two tofour second cooling periods were created, after which the tool unit 9and heating assembly 13 were raised, with the tool element working edge19 moving from cover 1 with a complete film-free separation.

Although shown with the induction heating coil assembly 13 locatedbeneath the web 5, the assembly may be above the web, but such anarrangement does not provide for convenient release of the film web asshown in FIG. 7. This may also create some softening of the adjacentfilm web and increase the transfer time of the conveyor 4 or the filmweb 5 during each complete cycle.

Altnough described with a particular inductive heating wherein a currentis induced in the tool element 18, other forms of remote or inducedheating may be also used. The present invention can also be applied toother materials and in other embodiments.

The tool element 17 is of course shaped in accordance with theparticular cutting and/or sealing function involved. For example, FIG.7a illustrates a tool end which has been applied to a cutting andsealing tool element. The tool element 17 in FIG. 7a has a relativelypointed cutting edge 35 with the inner bottom wall 35a inclined atapproximately 45 degrees while the outer wall 35b is inclined at a muchlesser angle to the vertical. The tool element of FIG. 7a has beenparticularly applied to cutting and sealing a foam pad member of a largedispersive body contact electrode in place by the simultaneouslypressure engagement and heating with a foam web to thermally sever andthen seal a severed pad member. Althgugh the tool unit is shown havingan annular cutting end member and a separate tubular heat transfermember, other constructions may of course be made within the teaching ofthe present invention.

A second embodiment of the invention is illustrated in FIGS. 8-9,inclusive, which is particularly directed to a procedure and apparatusfor attaching a smaller foam cover or pad 36 to a cup-shaped body 37,and particularly with the edge of the pad fusion bonded within a recess37a in a flat outer opening wall 38. The illustrated product of thesecond embodiment is shown in FIG. 8a, and is a uniquely formedpre-gelled body contact electrode, such as widely used for attaching ofelectrical instrument leads to a human body as a part of a medicaldiagnosis. The apparatus of the second embodiment is generally similarto that of the first embodiment. For purposes of simplicity and clarityof explanation, like elements of the two embodiments are identified bycorresponding numbers, and such common components are not againdescribed in detail in connection with the second embodiment. Thepre-gelled body contact electrode is shown including the main cup-shapedplastic body 37 which serves to retain an electrically conductive gel39. The gel 39 fills the cavity of the cup-shaped body 37 and saturatesfully or partly the foam pad 36 such that functional amounts of gel aredispersed throughout the pad, so as to provide satisfactory electricalcontinuity to a human body skin surface when the electrode is located inabutting relation to the skin. The body contact foam pad 36 is securedover the open end of body 37, and projects partly into the body cavity,as more fully described hereinafter. A metallic contact member or rivet39a is secured within the base of the body 37 and creates a lowresistance electrical path from the gel 39 to the exterior of theelectrode for connection to an appropriately shaped external connector,not shown. The external connector connects the electrode to anappropriate circuit.

The electrode assembly is suitably held in place at a desired locationon a patient's body by an attachment means. A typical means, shown inFIG. 8a, includes an attachment foam washer 40 having an exteriorpressure-sensitive adhesive coating 41 on the exterior face that iscompatible with and when pressed against the human body skin surface,firmly but releasably attaches the electrode to the skin. The attachmentwasher 40, usually formed of foamed spongy material, is securedencircling the body 37 by a back-up washer 42 secured to the back sideof body 37. Thus, the back-up washer 42 is a plate-like disc which issecured against the back of body 37 and the washer 40 by a suitableadhesive 43. The rivet 39a is shown having an outer flanged cap 44 whichalso abutts and firmly clamps the adjacent portion of the back-up washer42 in place. The cover 45 is shown as a disc-like plate or card somewhatlarger than the support washer 40. Cover 45 is adhesively attached by acoating which may be readily peeled off from pad 40 for attachment ofthe latter to the body.

The saturated gel pad 36 must be protected until the electrode is used,and in the illustrated embodiment is sealed by a thin film cover 47 ofsuitable plastic. The cover 47 is preferably a low density polyethyleneon the order of 9 mils thick to essentially prevent transmission offluid into or from the pad. Thus, the gel pad cover 47 is sealed to thefilm-like coating 46 on card 45 by an annular seal 48 to establish asubstantially fluid tight enclosure of the gel pad 36. The cover 47 isremoved simultaneously with the removal of the cover 45. The enclosurefor the gel-saturated pad 36 preferably at least approaches a hermeticseal to prolong the shelf-life of the final electrode unit. Thedescribed materials with the fusion bonding established by the presentinvention establish a unit having a significant commercial shelf life.

In the illustrated embodiment, the electrode unit is formed in a seriesof steps including the application of the foam pad 36 in the apparatusof FIGS. 8-9, the injection of the gel through the attached pad, andthen the application of the protective cover 47 in an apparatus such asshown in FIG. 1.

The conveyor 4 is formed with appropriate recesses 49 to receive thecup-shaped body 37 with the contact 39a in place. Generally, the foampad 36 is removed from a foam web 50 and moved by a tool unit 9downwardly, with the pad 36 removed and sealed to the cup-shaped member37 and particularly the flat top wall 38 by tool unit 9, generally as inthe manner of the previous embodiments. The foam pad 36 is formed ofpolyurethane which is not severed by downward movement of the cuttingedge of the tool element but only by the simultaneous heating of toolelement 17.

In the embodiment of FIGS. 8 and 9, the tool unit 9 and particularly thetool element 17 is formed with a cup-shaped cutting and sealing member51 having an appropriately shaped cutting end 52 and a mounting baseportion 53. The cutting and sealing member 57 is connected by a bolt 53awhich may be formed of stainless steel to a cooled heat sink member 54,which is suitably coupled to a power cylinder unit, not shown. In thisembodiment an additional annular clamp member 55 is shown secured as apart of the tool unit. The clamp member 55 is an annular member having acentral mounting base portion 56 secured between the heat transfermember plate and the base of the member 57. An L-shaped extension fromthe mounting portion 56 terminates in an outwardly extending leg orflange 57 which is located outwardly of the tool unit 9 and in overlyingrelationship to the induction heating unit or coil assembly 13. Theclamp member 55 is formed of a flexible but relatively firm rubber-likematerial or other like material, such as Kraton G 2705, manufactured andsold by Shell Chemical Company.

Induction heating assembly 13 of the second embodiment corresponds tothat previously described except that an outer non-metallic cover orshell 58 is such as an acrylic plastic or any other suitable material,shown provided on ring 30 within which the coil 31 is embedded.

In operation, the tool unit 9 again moves downwardly with the inductionheating coil assembly 13. In this embodiment, the annular flange 57 ofthe clamp member 55 moves downwardly onto the foam web 50 and forces thealigned web portion into engagement with the shell 58 of inductionheating coil assembly 13. The flange 57 may force the heating coilassembly 13 downwardly against conveyor 4 and compress the foam web asat 58a, as shown in FIG. 9, and thereby firmly grips the web about thecutting and sealing element 17. The separate cylinder 16 may then beeliminated.

The clamping engagement causes the deflection of the annular clampingmember 55, as shown in FIG. 9. Backing ring or washers 59 are shownsecured to the opposite faces of the mounting portion 56 of the clampmember 55 to provide a stop to the deflection of the leg 57. The backingring 59 functions to increase the clamping force and thereby to compressand firmly clamp web 58a in place during the cutting and sealingoperation. The clamp member 55 and associated washers 59 are formed of anon-metallic material to maintain the described heat transfer path tothe member 54.

As the tool unit 9 moves downwardly into engagement with the clampedfoam web 50, the edge 52 stretches the foam web 50 as at 59a in FIG. 9and forces the aligned portion of the foam web 50 downwardly intoengagement with the outer flat wall 38. When in engagement with wall 38,the induction heating assembly 13 is energized to inductively heat thetool element 17 which again functions to sever the foam pad 36 from theweb 50 and simultaneously heats the wall 38 to the softeningtemperature, such that tool edge 52 moves into wall 38 to form therecess 37a therein. The periphery of the foam pad 36 is, of course,simultaneously forced into the recess 37a formed in the wall 38 by thepressurized force of tool unit 9 and thermally welded in place.

The tool unit 9, and particularly element 17, is held in the cutting andsealing position with the induction heating coil unit 13 energized for asuitable sealing period. After the sealing period, the induction heatingcoil unit 13 is deactivated and the tool unit 9 held in position for acontrolled cooling period, during which the tool element 17 againrapidly cools as result of heat transfer through the base portion 53 andtransfer bolt 53a to the cooled member 54. After a short period toolunit 9 is raised from the foam pad 36 and wall 38 to release the coveredcontainer or cup-shaped body 37. In the illustrated embodiment, thecutting and sealing member 51 is located within the outer leg 57 of theclamp member 55. Thus, as the tool unit 9 returns to the raised orstandby position, the leg 57 tends to move the web 50 from the cuttingand sealing member 51. This action would further assure completeseparation of the web if there is any tendancy of the web to stick tothe member 51.

When the foam pad 36 is severed from the foam web 50 and the assemblyreturned to the loading position of FIG. 8, the web 50 returns under thetension force to the horizontal plane, with the inner severed portionlocated immediately beneath the clamping member 55. The heating coilassembly 13 moves upwardly with the tool unit 9 to allow the movement ofthe pad covered body 37 from the alignment with the tool unit. The toolunit 9 moves upwardly to the position of FIG. 8, thereby freeing thefoam strip or web 50 for longitudinal movement thereof and alignment ofa new portion within the cutting and sealing apparatus for a new cycle.

The pad-covered body 37 may then be immediately transferred to a stationto insert the gel through the pad 36 and into the cavity of body 37, andthen moved to a sealing station, such as shown in FIG. 1, to apply cover47. The cover 47 may of course be applied in any other manner suitablefor creating a hermetic-type enclosure of the gel-saturated pad 36.

This results in a simpler and less costly assembly. The moreconventional electrode includes a means for securing the gel pad withina cavity in combination with a multiple layered cover, attachment andpackaging assembly consisting of backing, sealing and outer protectiveelements. Generally a flanged cap is secured overlying the gel andfilled cup and held in place abutting a back-up card by an adhesivecoated label. Some care must be taken to ensure full area adhesion ofthe label to insure maintaining of the gel in a highly moist state andsatisfactory function in a medical diagnostic environment. The multiplepart assembly of the present invention with pressure sensitive adhesivelayers results in substantial reduction in material and assembly costs.Clearly the cover 45 and 47 which may be applied with this invention ismuch smaller and lighter than the previous complex multiple layerassembly and is sealed to the card 45 without the use of expensivepressure sensitive coatings. Further, the new film-like cover 47 mayconveniently be more transparent than the conventional cap and canproduce a more attractive product. Testing on the cover 47 attached by aheat seal 48 has shown good retention of moisture and prevention ofescape of the gel while realizing significant cost savings.

The method and apparatus of the invention described with the aid ofFIGS. 8-9, inclusive, are thus used to simplify the structure and reducethe costs associated with the attachment of the gel-foam pad 36. Theheat sealed foam pad 36, which is automatically cut from a web and heatsealed into a depression of the top face of the gel cup 37, as shown inFIGS. 8 and 8a, is retained in position to hold the gel 39 in the propermanner to make electrical contact without the need for any adhesive.Further, not only is the cost of the adhesive eliminated in the newprocedure, but the adhesive is removed from the key area under the foampad and minimizes possible interferences with the free flow of the gelwhen introduced into the foam pad and forcing the gel through the foampad 35 through the total area of the cup portion. The automatic cuttingand sealing in position by the tooling of this disclosure eliminatesmanual attention, thereby reducing manufacturing costs as well assimplifying the design of the product.

In summary, the present invention as shown incorporated in theembodiment of the invention of FIGS. 8-9 simplifies the manufacture andreduces the costs of both the electrode structure itself and theprotective packaging. The apparatus and process considered with respectto FIGS. 8-9, inclusive, of this disclosure also permits thesimplification of the design with elimination of the usual protectivecap assembly and interconnected multiple layered pressure sensitivelabel and attachment means. Further, a cover such as cover 47 may beapplied to a more conventionally assembled contact body and foam padunit which is constructed with a suitable plastic covered attachmentpad, or a supporting card.

Thus, the second embodiment is essentially similar to that of the firstembodiment in providing for simultaneous cutting and sealing of a firstelement formed of plastic or other compatible material to a secondelement by a thermal or fusion bond.

The present invention, particularly with the controlled cooling of thetooling may also be advantageously applied to either cutting or shapingof elements, or the direct thermal sealing of preformed element toanother. An embodiment of the invention for sealing of a preformedmember to another member is illustrated in FIG. 10.

In this embodiment of the invention, a preformed hat shaped cap 60 isadapted to be located over an article 60a. The cap includes a flangeportion 60b thermally sealed and attached to a base member 61 using atool unit 62. The modified tool unit 62 is generally similar to thepreviously described embodiments and includes a cooling plate and atubular heat transfer element to which a specially shaped sealing foot63 is secured. The sealing foot 63 is an annular L-shaped memberdefining a lateral enlargement. In this instance, the bottom wall of thefoot is formed with a flat bottom to develop a seal of a particularwidth. The inner edge of the sealing foot is provided with a chamferededge portion 64 to provide the desired seal width while locating of theworking enlargement radially outwardly of the balance of the tool unit62 and thereby locate the enlargement closely adjacent to the annularheating coil assembly 13.

In the illustrated embodiment of the invention, a holding ring 65 issecured within the heat transfer element 21. The holding ring 65 isgenerally a cup-shaped member having a base 66 interconnected to thecooling plate 23 by a suitable threaded stud 67. The ring 65 projectsdownwardly beyond the transfer member 21 but terminates inwardly of theouter sealing face of sealing foot 63. The holding ring 65 serves tolocate and center the preformed cap 60 in position and simultaneouslycontrols extrusion of the flange 60b under the clamping action of thetool element 17.

In the embodiment of FIG. 10, release of the tool element 17 from thesealed cap 60 is assisted by a spring loaded knockout pin 68 which ismounted coaxially within the threaded attachment stud 67. A springmember 69 within the stud 67 biases the knockout pin 68 outwardly.During the downward clamping movement, the pin 68 engages the top of thepreformed cap 60 and spring 69 is compressed during the final movementof the tool unit 62 into the sealing position.

During the initial release of the tool unit, pin 68 is biased outwardlyby the spring 69 to positively hold cap 60 in place, thereby assistingin the release of the holding ring 65 and the sealing foot 63 in theevent there is any tendency for such elements to stick to the preformedcap. The holding ring 65 and pin 68 are preferably formed of material tominimize induction heating thereof.

The final result is an outer peripheral sealed portion 70 generallycorresponding to the width of the sealing foot 63 and an inwardlylocated enlargement which is formed as at 71 by movement of theheat-softened plastic flange material upwardly around the holding ring65. A practical application of the invention shown in FIG. 10 would bethe attachment of the usual preformed cap of a body-contact electrode tothe pad or gell filled cup of the prior art construction in place of theusual label with its pressure sensitive adhesive.

As in the previous embodiments, inductive heating of the tool unit 62permits very accurate control of the heating, and not only of the levelof heating but the sequence of heating. Further, the heat transferelement 21 and the associated cooling means provide the desired rapidcontrolled cooling of the inductively heated tool element upon thetermination of the sealing cycle.

Still a further embodiment of the invention is illustrated in FIGS.11-13, wherein a cup-shaped plastic container 72 having an outer flange73 is sealed by a sealing liner 74 which is fusion bonded to the flange73. The sealing liner 74 is shown coated with an adhesive layer 75formed of a suitable material which melts and bonds the adjacent flange73 when properly heated. The liner may produce a hermetic closure of thecontainer 72 for protecting the contained products from the surroundingenvironment and the like. Generally, in such a package, the liner 74 maybe a relatively thin element which may be readily damaged or disruptedduring handling, storage and the like. A plastic lid 76 of a relativelyheavy supporting material is desirably provided. The illustrated lid 76includes a downwardly projecting resilient lip 77 which snaps over theflange 73 to secure the lid 76 in protective overlying engagement tosealing liner 74. The covered container 72 is completed by thermallyattaching the liner 74 in place.

As shown in FIG. 11, a turntable 77a which is adapted to rotate betweena plurality of stations, is shown as four equicircumferentially spacedstations, including a loading and unloading station 78, a heating andsealing station 79, and a pair of cooling and final sealing stations 80and 81. The station 78 is shown constructed for both loading of anunsealed container assembly and unloading of a sealed containerassembly, and includes a table 82 having a supply of assembled containerunits 83 and an unloading table 84 for receiving of sealed container 85.An operator 86 inserts and removes the container, which may be a humanoperator or an automated machine operator.

The present invention is particularly directed to the construction ofthe inductive heating apparatus which is operable at station 79. In thisembodiment of the invention, four separate tool units 87 are secured tothe turntable unit in circumferentially spaced relation in accordancewith the spacing of the several stations 78-81. The turntable 77a isindexed by a suitable stepped driving means, not shown, through steps of90 degrees to sequentially transfer each of the tool units 87 to thenext adjacent station. A dwell period is included to hold the tool unitsat the aligned station for a predetermined period sufficient to completethe maximum work requirement, and in particular to permit proper loadingand unloading at station 78, proper heating to effect sealing of liner74 to flange 73 at station 79 and cooling at the subsequent stations 80and 81.

The liner attaching apparatus includes a tool unit 87 which is againinductively heated and separately cooled, As shown in FIG. 12, the toolunit 87 is an inverted tubular tool assembly which has a cooled plate 88secured by bolts 89 or suitable means to fixedly attach the tool unit 87to the turntable 77a.

A tubular heat transfer element 90 is secured to the cooling plate andprojects upwardly therefrom. A heating ring 91 is secured to the outerend of the transfer element 90. The transfer element 90 and the heatingring 91 are formed of a generally similar diameter which is selected tolocate the ring beneath flange 73 of the cup-shaped container 72. Thecontainer assembly with the lid 76 lightly holding the sealing liner 74in position is mounted at loading station 78 within the tool unit 87,with flange 73 resting on the heating ring 91.

A pressure cap 92 is secured at the loading station 78 overlying theinserted capped container assembly to force and hold the sealing liner74 and lid 76 in firm engagement with the outer surface of the flange 73during the movement through the heating and sealing apparatus. In theillustrated embodiment of the invention, the pressure cap 92 is a thinnon-metallic, flat member having an inner end pivotally mounted toturntable 77a to the inner side of the tool unit 87, as at 93. Cap 92has a width slightly greater than the overcap and is provided withdepending front and back walls spaced to appropriately hold the overcap76 and therefor container 72 within and beneath the pressure cap 92. Thepressure cap 92 is securely and releasably locked in the clampingposition before the indexing to the station 79 by a suitable holdingmeans, such as by spring loading of the pivot shaft as at 94. Othermeans may of course be used.

The heating and sealing station 79 includes a fixed induction coil unit96 which may include a flat multiple turn coil 97 in a plane immediatelyabove that of the loaded tool unit 87, and particularly immediatelyabove the plane of the latched pressure cap 92. The coil unit 96 is ofcourse connected to a suitable RF power supply, not shown, to establisha magnetic field 98 which passes downwardly through the pressure cap 92,the lid 76, the liner 74 and the flange 73 into and through theinduction heating ring 91. The ferromagnetic ring reacts with thecreation of induced eddy currents within the ring. The current generatesohmic and magnetic losses appearing as heat in the ring. After a fewseconds depending upon the design, the excitation level and the like,the temperature of the ring rapidly rises to the softening temperatureof the adhesive material 75 on the liner 74. As the result of the heattransfer from the heated ring 91 through the flange 73 directly intocoating 75, the adhesive coating material melts. The flange 73 isclamped in place and is sufficiently thick that the heat transfer isreadily accomplished without distortion of the flange as a result of theshort heating period. The coil 97 is deenergized at the end of theheating period and tool unit 87 quickly cools as the heat dissipatesthrough the transfer element 90 to the cooling plate 88.Correspondingly, the melted coating 75 of the lid 74 solidifies by heattransfer to the cooling ring.

As soon as the coil 97 is deenergized, the turntable 77a may be indexedto move the heated assembly to the first cooling station 80 while movinga newly loaded assembly 72 into alignment with the induction heatingstation 79. The proper timing of the assembly including the energizationof the heating coil, the movement of the indexing table and the like,can of course be readily provided through any suitable automatic controlmeans.

Although a cooled heat sink plate is shown in the several embodiments,other cooling means might be used. For example, a cooled fluid mediummight be moved directly over the outer removed end of the heat transfermember, such as fan generated air, for controlling the heat transferfrom the working or forming end of the tool element.

The illustrated embodiments are described with the use of inducedcurrent flow in the tool element creating heat as a result of magneticand ohmic losses. Other induced reactions which might be usable bysuitable selection of material and combinations, such as hysteresislosses, dielectric losses and the like as well as any other operableenergy field. The terminology "inductive" heating and similarterminology is therefore used herein to generically define heating basedon the creation of a changing high energy field which when coupled to atool element of an appropriate material interacts to create heat withinthe element. Although within the broadest aspect of the preferred multipart tool, direct energization such as direct conductive connection ofan electric power or even thermal power to the working end portion ofthe tool element might be used, such heat source is not considered asuseful as the inductive heating which permits rapid, effective controlof the concentration of the heat within the working or forming endportion of the tool element, as disclosed in the preferred embodimentsof the invention.

The present invention particularly in the preferred embodiments,provides a reliable, rapid and effective means of working plasticmembers, and particularly for cutting, forming and sealing in asimultaneous single tool operation.

Various modes in carrying out the invention are contemplated as beingwithin the scope of the following claims, particularly pointing out anddistinctly claiming the subject matter which is regarded as theinvention.

We claim:
 1. A multiple part assembly including an enclosure for a moist pad member, comprising a cup-shaped container, heat seal means securing the outer edge of said moist pad member in the container, a support means secured to and encircling said container and including an annular backing member encircling said open end of said container and adhesively affixed and peelable from said support means, a plastic film cover overlying said pad member and adjacent portion of the backing member, and an encircling fusion seal joining said plastic film cover to said backing member for removal of said cover with said backing member. 